Fuel injectors are used to inject fuel into the combustion chambers of internal combustion engines. A fuel injector typically comprises an injector body, an injector nozzle and an injector needle. The injector needle is movable relative to a nozzle seat formed in the injector nozzle to control the injection of fuel into the combustion chamber. One technique for controlling operation of the injector needle utilises a control valve to control the fuel pressure in a control chamber. The control valve typically comprises a control valve member for controlling fluid communication between the control chamber and a backleak circuit. The control valve member has a valve face for cooperating with a valve seat. The control valve member is fixedly connected to an armature which is disposed in an armature chamber. An electro-mechanical actuator generates a magnetic field to displace the armature, thereby controlling operation of the control valve. The actuator is operable to control the control valve member to lift the valve face from the valve seat to open the control valve; and to seat the valve face in the valve seat to close the control valve.
When the control valve opens, high pressure fuel enters the armature chamber from the control chamber. The introduction of fuel into the armature chamber can cause cavitation in the fuel and/or apply a jet impact force on the armature. These can affect operation of the control valve, for example resulting in variations in the operation of the control valve in a series of injections.
At least in certain embodiments the fuel injector according to the present invention seeks to overcome or ameliorate at least some of the aforementioned problems.